Excel is known to work
I believe the answer is:
outdo
'excel' is the definition.
(thesaurus)
'known to work' is the wordplay.
'known' becomes 'out' (I've seen this before).
'to work' becomes 'do' ('do work' can be a synonym of 'work'**).
'out'+'do'='OUTDO'
'is' acts as a link.
(Other definitions for outdo that I've seen before include "Cap" , "Beat" , "Surpass, go one better than" , "Get the better of" , "Overcome" .)